The objective will be to determine how the quantities of two major dietary nutrients, protein and lipid, interact to influence 7,12-dimethylbenz(a)anthracene (DMBA) mammary carcinogenesis in rats. Different concentrations of dietary protein and lipid will be fed in casein-containing diets with the following micrograms of protein per kilocalorie of dietary energy: 20, 30 and 80. Lipid will be supplied as corn oil at 13, 26 and 54 micrograms per kilocalorie of dietary energy at each of three dietary levels of protein. Minerals, vitamins and fiber will be supplied at a constant ratio per kilocalorie of dietary energy for all dietary treatments. Experiments are designed to study dietary influences on the initiation and promotion phases of carcinogenesis. The absorption, tissue distribution and excretion of DMBA and its metabolites will be determined. Binding of DMBA metabolites to RNA, DNA, and protein of mammary tissue will be studied. Metabolites in urine and feces will be identified and quantitated. Liver aryl hydrocarbon hydroxylase and related mixed function oxidase components will be assayed to determine how the dietary variables influence their activity. All tumors will be studied histologically.